Polk PA4A Oscilloscope Testing

[FloJet]

You always have to start something. Clipping is clipping regardless of frequency. A lot of rap music is extremely poorly recorded. This is well documented.

Yup I don't like you and you always say stupid ass shit.

Poorly recorded????

YOU REALLY IS A DUMBASS HUH?

 

[Mainah]

I am not going to pretend to know anything about the recording of music. I did test with multiple tones, sweeps, and white noise. There was very little variation in clipping from the RCA outs across all tests. The signal does distort at the speaker level outputs from both the head unit and amps. I am not trying to win any competitions but rather get the most out of what I have safely. With m 400/4 amps and bridging I am not going to come close to overloading the 1040 mm subs but I also don't need to feel sick to my stomach from insane bass or chew through electrons too fast. For me the now enclosed in hull subs being able to make the every panel in the boat oscillate while sounding deep, clean, rich, and being balanced with the mids and highs makes me pretty darn happy.

I will post more on it but those with bone stock systems with the Polk PA4A should not turn up the volume past 90% as that is where clipping occurs at the speaker level outs. It does not take lots of amps to make it lots better. I only have two 4 channel amps and a few more speakers and the difference is night and day.

 

[Bruce]

Yup I don't like you and you always say stupid ass shit.

Poorly recorded????

YOU REALLY IS A DUMBASS HUH?

Please review Our Code of Conduct and adhere to it.

 

[adrianp89]

I am not going to pretend to know anything about the recording of music. I did test with multiple tones, sweeps, and white noise. There was very little variation in clipping from the RCA outs across all tests. The signal does distort at the speaker level outputs from both the head unit and amps. I am not trying to win any competitions but rather get the most out of what I have safely. With m 400/4 amps and bridging I am not going to come close to overloading the 1040 mm subs but I also don't need to feel sick to my stomach from insane bass or chew through electrons too fast. For me the now enclosed in hull subs being able to make the every panel in the boat oscillate while sounding deep, clean, rich, and being balanced with the mids and highs makes me pretty darn happy.

I will post more on it but those with bone stock systems with the Polk PA4A should not turn up the volume past 90% as that is where clipping occurs at the speaker level outs. It does not take lots of amps to make it lots better. I only have two 4 channel amps and a few more speakers and the difference is night and day.

I know this stuff interests you, so if you get some free time, google "Loudness Wars" to find out more about how the quality of recordings has degraded over time. The basis of this gets much worse in certain genres, especially with amateur mixers handling some of today's more popular music. An example of this would be up and coming rappers who cannot afford to pay a quality engineer to master their tracks.

https://www.npr.org/2009/12/31/122114058/the-loudness-wars-why-music-sounds-worse

 

[Hector]

Just curious on what’s the difference in going from the stock radio straight to the amps vs going stock radio to ws420 to the amps in terms of signal being fed to the amps? Is the 420 automatically boosting the signal to 4v?
What if one bypassed the stock radio all together and used the aux in from the ws420

 

[Mainah]

The ws420 bt has a few things going for it. One is internal potentiometers. Another is aptx bluetooth. My guess it that bypassing the polk unit amd going directly into the ws420 bt with either aux in or bluetooth with net a better result than the polk. Not to mention the multiple zones and talkback mic. Now just to find someone to let me test and tune their ws420 to find out for sure.

 

[Hector]

The ws420 bt has a few things going for it. One is internal potentiometers. Another is aptx bluetooth. My guess it that bypassing the polk unit amd going directly into the ws420 bt with either aux in or bluetooth with net a better result than the polk. Not to mention the multiple zones and talkback mic. Now just to find someone to let me test and tune their ws420 to find out for sure.

Shame we are 6 hours away.
Ironically I could swear my system sounded better before I added the ws420. I didn’t get the bt model because I figured I would never need it, fast forward one season and the bt on my radio goes out. I ordered this https://www.crutchfield.com/p_13691126/JL-Audio-MBT-RX.html?tp=61776&awkw=79438365495&awat=pla&awnw=g&awcr=65372638345&awdv=t&awug=9008422&gclid=EAIaIQobChMI54C9jPiS2gIVF0sNCh2XdQQlEAQYAiABEgIppvD_BwE and am installing this weekend.

 

[Jgorm]

@Mainah
Did you test both 1k and 40k tones? I believe you shouldn't get the same clipping rate with both tones. One would need to compensate for the 40k tone as that should clip before the 1k.

40kHz? Double what humans can hear? So the dogs and bats can appreciate the music?

 

[GTBRMC]

I don't know if he spends much time on here any more, but @David Analog might have some input on the technical side of this discussion.

Also, @Earmark Marine sold me on the merits of the WS420BT... including higher voltage output and high quality Bluetooth. I sold the boat last summer, but the great, trouble-free performance and convenient zone volume control over a couple of seasons I spent with the WS420BT demonstrated its value to me many times.

 

[swatski]

Ironically I could swear my system sounded better before I added the ws420.

I must say I have had one somewhat similar experience - now that you mentioned that - with the subwoofer. Very strange - my Infinity Basslink powered sub was noticeably more responsive at low volumes before I hooked up the WS420. Now - I have it cranked up all the way most of the time and it is okay and comes alive at higher volumes, but it did appear to have lost some of it's low volume mojo.

With that, I would never want to get rid of the WS420 - and lose the ability to turn the main volume on or off with one external knob, and balance the zones.

--

 

[adrianp89]

I would really want it for the megaphone feature, so I can call out people going fast in a no wake zone.

 

[Mainah]

40kHz? Double what humans can hear? So the dogs and bars can appreciate the music?

I assumed 40hz as it is a common test tone for sub channels.

 

[Mainah]

I must say I have had one somewhat similar experience - now that you mentioned that - with the subwoofer. Very strange - my Infinity Basslink powered sub was noticeably more responsive at low volumes before I hooked up the WS420. Now - I have it cranked up all the way most of the time and it is okay and comes alive at higher volumes, but it did appear to have lost some of it's low volume mojo.

With that, I would never want to get rid of the WS420 - and lose the ability to turn the main volume on or off with one external knob, and balance the zones.

--

I bet adjusting the internal pots will solve for that. A dmm can be used to make sure not outputting too much voltage. Just make sure it is not a bargin bin one.

 

[FloJet]

40kHz? Double what humans can hear? So the dogs and bars can appreciate the music?

Yes typo. I meant 40 hz lol. 1kz for highs 40 hz for lows for tuning.

 

[FloJet]

I must say I have had one somewhat similar experience - now that you mentioned that - with the subwoofer. Very strange - my Infinity Basslink powered sub was noticeably more responsive at low volumes before I hooked up the WS420. Now - I have it cranked up all the way most of the time and it is okay and comes alive at higher volumes, but it did appear to have lost some of it's low volume mojo.

With that, I would never want to get rid of the WS420 - and lose the ability to turn the main volume on or off with one external knob, and balance the zones.

--

Sounds like you need to tune the connext and WS420 higher. Than you will still more hump at low volumes. Maybe get with @jcyamaharider about tuning the WS420 internally. I have explained to him some of the process in doing so. You will be amazed when done correctly.

For example. I have my WS420 tuned to have it at full volume. rather than 3/4ths of the way. Its a line driver so you can really push it.

 

[Mainah]

I completed step 2 of tuning my system yesterday afternoon. First a couple of notes about the data. My portable mini digital oscilloscope samples at a 72 mhz rate stores up to 4096 frames in memory computes buffers the data to the buffer setting reads computes frequency based on x and y the renders the screen. This is important because you will notice in the screenshots an exaggerated view of the wave form and when when the buffer is set such that less than three peaks and valleys are in the x,y then frequency won't be computed. USB input was used for the testing/tuning with everything tuned flat. The screen grab saved file numbers you see are something I have to manually enter and I was keeping track with pen and paper. I did arrow over a bit too much at times so the sequence may be a bit off from what is described by those are the right screen grabs for the description.

Polk PA4A Speaker Level Outs-

90% volume with USB input was the max pre clip with a 1k test tone netting 9.4 volts. I did not get the screen grab but also no clip at 40 hz. Turning on loudness caused clipping and distortion at 90% so going forwards I am going to keep loudness off. The wave form is rather clean which I found surprising but my cabin speakers can handle much more voltage. I have 6 speakers tuning off the Polk speaker level outs (bow Polk MM651, swim deck Polk MM651, stock tower tweeters) given that I prefer those areas to be a bit quieter and the speakers are receiving full bandwidth (except the towers tweeters) I feel good about this.



JL M400/4 with 80k High Pass Filter-
I have 4 mid cabin Polk MM 651 running off of 4 channels. The first thing you will notice is that the waveform is no longer clean. This is being primarily caused by my oscilloscope picking up the PWM distortion of the signal inherent in all Class D amps. Amplifiy the noise already in the signal is also a part of this. Keep in ming this is exaggerated given the sample rate, sample size, and buffering. 14.4 volts was the max pre clip voltage (I am using a 10x probe at this point to see more detail on the screen so 1.44*10 =14.4). I zoomed in on the wave form in the second photo by increasing the buffer. The speakers could handle more voltage but I am satisfied with this.



JL M400/4 with 120k Low Pass Filter Bridged-
I am running two Polk 1040MM subs of of two bridged channels each. As noted above the distortion is being primarily caused by PWM and the oscilloscope is picking up on it because of the setting I am using. 40hz at 33.6v (again 10x probe was being used) was causing a very slight clip seen the the leading edge of the valley and trailing edge of the peak. I increased the buffer to see the wave form in more detail and fine tuned this to 30.4v. These subs could handle a lot more and maybe someday I will get a more powerful amp for them but for now I am happy with this.



How it sounds-
I did not want to tick off the neighbors for too long but I had to hear how it sounded. I was quite happy with the balance across the lows and mids. The high seemed a bit bright so I may need to turn down the treble in the POLK head unit. I found that a cranked 39.5hz test tone was just about resonant frequency for the boat as a whole and it gave me a mild sick to my stomach feeling. I could actually see the boat hull oscillating in spots without having to look too close. No bad vibrations of anything playing a few different tracks. For this year I will be happy with it and will see if I go another step up down the road. I still need to some sound db and sound spectrum stuff out on the water so I don't tick off my neighbors and the hull being in the water may change the sound dynamics a bit.

 

[Mainah]

One more quick note. The gains on JL amp end up slightly less than half for both the cabins and the subs.

 

[FloJet]

I completed step 2 of tuning my system yesterday afternoon. First a couple of notes about the data. My portable mini digital oscilloscope samples at a 72 mhz rate stores up to 4096 frames in memory computes buffers the data to the buffer setting reads computes frequency based on x and y the renders the screen. This is important because you will notice in the screenshots an exaggerated view of the wave form and when when the buffer is set such that less than three peaks and valleys are in the x,y then frequency won't be computed. USB input was used for the testing/tuning with everything tuned flat. The screen grab saved file numbers you see are something I have to manually enter and I was keeping track with pen and paper. I did arrow over a bit too much at times so the sequence may be a bit off from what is described by those are the right screen grabs for the description.

Polk PA4A Speaker Level Outs-

90% volume with USB input was the max pre clip with a 1k test tone netting 9.4 volts. I did not get the screen grab but also no clip at 40 hz. Turning on loudness caused clipping and distortion at 90% so going forwards I am going to keep loudness off. The wave form is rather clean which I found surprising but my cabin speakers can handle much more voltage. I have 6 speakers tuning off the Polk speaker level outs (bow Polk MM651, swim deck Polk MM651, stock tower tweeters) given that I prefer those areas to be a bit quieter and the speakers are receiving full bandwidth (except the towers tweeters) I feel good about this.

View attachment 70955

JL M400/4 with 80k High Pass Filter-
I have 4 mid cabin Polk MM 651 running off of 4 channels. The first thing you will notice is that the waveform is no longer clean. This is being primarily caused by my oscilloscope picking up the PWM distortion of the signal inherent in all Class D amps. Amplifiy the noise already in the signal is also a part of this. Keep in ming this is exaggerated given the sample rate, sample size, and buffering. 14.4 volts was the max pre clip voltage (I am using a 10x probe at this point to see more detail on the screen so 1.44*10 =14.4). I zoomed in on the wave form in the second photo by increasing the buffer. The speakers could handle more voltage but I am satisfied with this.

View attachment 70956 View attachment 70957

JL M400/4 with 120k Low Pass Filter Bridged-
I am running two Polk 1040MM subs of of two bridged channels each. As noted above the distortion is being primarily caused by PWM and the oscilloscope is picking up on it because of the setting I am using. 40hz at 33.6v (again 10x probe was being used) was causing a very slight clip seen the the leading edge of the valley and trailing edge of the peak. I increased the buffer to see the wave form in more detail and fine tuned this to 30.4v. These subs could handle a lot more and maybe someday I will get a more powerful amp for them but for now I am happy with this.

View attachment 70958 View attachment 70959

How it sounds-
I did not want to tick off the neighbors for too long but I had to hear how it sounded. I was quite happy with the balance across the lows and mids. The high seemed a bit bright so I may need to turn down the treble in the POLK head unit. I found that a cranked 39.5hz test tone was just about resonant frequency for the boat as a whole and it gave me a mild sick to my stomach feeling. I could actually see the boat hull oscillating in spots without having to look too close. No bad vibrations of anything playing a few different tracks. For this year I will be happy with it and will see if I go another step up down the road. I still need to some sound db and sound spectrum stuff out on the water so I don't tick off my neighbors and the hull being in the water may change the sound dynamics a bit.

Very interesting read. Ya no properly tuned system should ever have to use the loudness or bass boast feature. It always introduces too much clipping in my experience. And I always leave EQ on flat to tune and fairly adjust it after tuning.
When you test the speaker level output, are you referring to using the speaker wires? In the past I've noticed you will get slightly different results that way due to low impedance speaker wiring that they install on our boats. One reason I have ran all new speaker wiring. Because of this I've aways tuned throught the RCA signal. But now I need to check the speaker level if that's what you are doing. Also with the test tones you are using, are they .Wav extensions on your phone? I've found you will get slightly different results using .mp3, .mp4 or ect. As you probably already know, .WAV is best quality you can download to use besides using the actual CD. So this is where recording source is value important. The tuning stage.

Now the craziest thing about your experiment is that you are not getting any clipping at 40 hz? Thats crazy to me. Usually 40 hz will clip before the 1khz tone in my experience. Now I have to play around with this more. Lol. I've only got them to be even clipping once or twice. But this is hard to say since I'm using the WS420 as buffer between the amps and the Polk system.

I too believe you will get different sound dynamics on the water as now you will be in open air with more resonating nature sound around you. This is where I believe we all try to achieve more output as open air sucks the sound out of the boats.

I wonder with a semi line driver like the WS420 in use if your results will vary through the speaker output. ​

 

[adrianp89]

One more quick note. The gains on JL amp end up slightly less than half for both the cabins and the subs.

Exactly how my Kicker ended up. Again great info. This should probably be stickied.

 

[Mainah]

Very interesting read. Ya no properly tuned system should ever have to use the loudness or bass boast feature. It always introduces too much clipping in my experience. And I always leave EQ on flat to tune and fairly adjust it after tuning.
When you test the speaker level output, are you referring to using the speaker wires? In the past I've noticed you will get slightly different results that way due to low impedance speaker wiring that they install on our boats. One reason I have ran all new speaker wiring. Because of this I've aways tuned throught the RCA signal. But now I need to check the speaker level if that's what you are doing. Also with the test tones you are using, are they .Wav extensions on your phone? I've found you will get slightly different results using .mp3, .mp4 or ect. As you probably already know, .WAV is best quality you can download to use besides using the actual CD. So this is where recording source is value important. The tuning stage.

Now the craziest thing about your experiment is that you are not getting any clipping at 40 hz? Thats crazy to me. Usually 40 hz will clip before the 1khz tone in my experience. Now I have to play around with this more. Lol. I've only got them to be even clipping once or twice. But this is hard to say since I'm using the WS420 as buffer between the amps and the Polk system.

I too believe you will get different sound dynamics on the water as now you will be in open air with more resonating nature sound around you. This is where I believe we all try to achieve more output as open air sucks the sound out of the boats.

I wonder with a semi line driver like the WS420 in use if your results will vary through the speaker output. ​

I am using an app (f Generator PRO V4.1.0) to generate the test tones on the fly. I believe this is outputting 160 Kbps MP3 over the USB connection. I do believe that clipping is occurring earlier at 40hz but the volume control on the PA4a is far from linear and closer to exponential which is why I likely did not observe that. Final speaker level out to all speakers being driven must be tested. sound is produced be sending alternating current to the speakers. The frequency of that alternating current is what dthe magnet reacts to causing the speaker to move in and out. More voltage means the magnet will produce more push and pull at that frequency. More voltage = louder to a point. I tested the speaker level outs on the Polk head unit because I am using that to drive some of the speakers otherwise it is not needed. I did run new 14 or 12 awg knukonceptz speaker wire to all of the speakers. My testing so far has been done in my driveway with the bimini stowed. I would love to test a ws420 to see what gains can be had but have not committed to buying one as of yet. I really like the large Connext jog dial for controlling volume (quick to crank it when once the boarder is up and engines are high rpm then turn quick to reduce the volume once throttled down) all without having to look.